It is good practice to break any organizations storage requirement into
different “classes” of storage, where some data is stored on high performance
storage devices whereas less critical data, or where the resilience, time to
recover, or the speed of access is lower, is stored on lower cost storage
devices.

We refer to this as a Tiered Storage Model.

Classifying data enables IT managers to create tiered storage that matches
the business value of the data with the corresponding price/performance layer
of storage. For example, mission-critical applications might reside on high-
performance disks, while important but less critical data resides on less costly
ATA disks.